Wireless communication has undergone tremendous development and growth in the last few decades. Current digital wireless telephone networks based on multiple access techniques such as CDMA, FDMA or TDMA can offer high quality voice communications. However, these networks are not efficient at offering data communications when a number of users must be serviced, and a sharp increase in demand for data communications over wireless networks is expected.
For example, the IS-95 standard for CDMA networks can offer a maximum data rate of 9.6 kilobits per second (kbps) or 14.4 kbps depending on the selected service. As known to those of skill in the art, however, these rates are generally too slow to meaningfully accommodate modern data applications, such as web-browsing, streaming media and/or file transfer. Attempts have been made to increase the maximum data rate within IS-95. For example, U.S. Pat. No. 5,930,230 to Odenwalder teaches a high data rate CDMA wireless communication system that offers certain improvements over IS-95. However, Odenwalder is directed to the CDMA environment, and primarily contemplates the transfer of data from subscriber stations to base stations, (typically referred to as the “uplink” or “reverse” channel) and thus does not address the need for increased transmission of data from base stations to subscriber stations (typically referred to as the “downlink” or “forward” channel).
Another difficulty exists with IS-95 type networks in that they assign a dedicated communication channel between the base station and a subscriber unit and therefore the bandwidth of the dedicated channel is unavailable to other users in the network, even when no data is being transmitted between the base station and the subscriber unit. Thus, for connectionless services such as Internet Protocol (IP) networks, such a system does not typically provide effective use of limited shared bandwidth, which is a necessity for servicing large numbers of users.
Further, the characteristics of the data transmission typically are independent of the reception levels experienced at the receiver. Thus, the transmission characteristics are set to a lowest common denominator which is selected to ensure reception under worst case, or near worst case, conditions and is held constant for all transmissions. While this allows for simple system design and operation, it does not make efficient use of bandwidth or other system resources.
U.S. Pat. No. 5,949,814, also to Odenwalder (“Odenwalder #2”), teaches a system which provides a high data rate supplemental channel for CDMA telecommunications systems. In this scheme, the transmission system includes an in-phase channel set and a quadrature-phase channel set. The in-phase channel set provides a set of orthogonal medium rate control and traffic channels and the quadrature-phase channel set provides the high-rate supplemental channel and an extended set of medium-rate channels that are orthogonal with respect to each other.
While Odenwalder #2 can increase the downlink data transmission rate, it is not generally suitable for transmitting data to multiple subscriber stations, which have different abilities to receive the transmission. Further, Odenwalder #2 requires certain overhead control communication between the base station and the mobile user in order to commence a high data rate communication therebetween. Such a system is not well suited to systems such as packet-based communication systems where small amounts of data may need to be transferred to users as the necessary overhead can make the communication inefficient relative to the amount of data transferred. Similarly, such a system is not well suited to situations wherein a variety of users need data transmitted to them.